This invention relates to methods of isotope separation and enrichment and more particularly to methods of isotope enrichment wherein molecular species containing a particular isotope are selectively excited by infrared laser light sufficiently to undergo chemical reactions whereas unexcited molecules of the species do not.
The present invention is related to the invention disclosed and claimed in the applicants' previously filed U.S. patent application Ser. No. 570,924, entitled "Laser Isotope Separation by Multiple Photon Absorption," now U.S. Pat. No. 4,049,515. The invention described therein includes the selective multiple photon absorption by molecular species of a single wavelength of laser radiation with subsequent chemical reaction of the resulting excited species. This patent application is a continuation of application Ser. No. 354,417 filed Mar. 3, 1982, now abandoned, which was a continuation of application Ser. No. 913,635 filed June 8, 1978, also abandoned.
It is known in the art that lasers may be used to selectively induce chemical reactions which effectively result in isotope separation or enrichment; see, e.g., N. V. Karlov, "Laser-Induced Chemical Reactions," Applied Optics, vol. 13, p. 301 (1974). A preferred approach has been two-step irradiation by two lasers of differing wavelength. The first laser, which is usually indicated to be an infrared laser, is used to selectively excite those molecules of a compound containing a particular isotope of an element. The second laser, which is usually indicated to be an ultraviolet laser, is used to further excite these molecules sufficiently for them to undergo a chemical reaction. As a practical matter, it is difficult to make the second laser as selective in its action as is the first laser so that it tends to excite all molecules of the compound containing the element of interest. Accordingly, for isotope separation or enrichment, a rather severe constraint placed on this second laser is that it be of a wavelength such that the combined excitation produced by it and the first laser is sufficient to induce chemical reaction, but the excitation produced by it alone will not induce chemical reaction. Heretofore the art has not taught that the first infrared laser, even if sufficiently intense, permits any more freedom of choice of the photon energy of the second laser, than the photon energy of the infrared laser. It certainly has not taught that if the infrared laser is sufficiently powerful it may readily eliminate any need for the second laser at all.
It is known that through use of single-photon absorption leading to photodissociation, selective or preferential laser-induced chemical reaction useful for isotope separation or enrichment may be achieved. The art teaches that for this single-photon technique, lasers operating in the visible or the ultraviolet are required.
A major disadvantage of the use of visible or ultraviolet lasers in the single photon or two-step process is that the cross sections for direct, single photon absorption of light in these regions of the spectrum are quite small. In addition, it is quite difficult to achieve high laser power operation with any efficiency in these regions of the spectrum.